The present invention relates to an optical disk in which information is recorded both on land and groove tracks.
The invention also relates to an optical disk drive device using such an optical disk.
More particularly, the invention relates to recognition patterns used for recognition of the header part provided in front of each information sector.
In conventional phase-change type optical disks, data is recorded only on grooves, and lands serve to guide the light spot for tracking, and to reduce crosstalk from adjacent groove tracks. If data is recorded on lands as well, the track density can be doubled on condition that the width of the grooves and the width of the lands are both unchanged. It has been discovered that the crosstalk between adjacent land and groove tracks is reduced if the difference in height between the lands and grooves is xcex/6 (xcex being the wavelength of the light source). Because of this discovery, the use of both land and groove tracks has become feasible. The use of both land and groove tracks is also advantageous with regard to the ease of mastering of the disk: it is easier to attain a certain recording density by the use of both land and groove tracks than by reducing the track pitch using only the groove tracks.
For instance, in the case of optical disks for use as computer data files, optical disks in which data is recorded both on land and groove tracks, and the tracks are concentric, so that after recording of one revolution (on a groove track, for example), a track jump is effected to start writing on the adjacent track (a land track). Sectors are managed in accordance with the sector addresses. Accordingly, the operation for recording and reproducing data, such as computer data, which need not be continuous, can be carried out without difficulty.
Rewritable optical disks are however also used for recording continuous data such as motion picture, or music. In multimedia applications (where computer data and video and audio data are mixed), spiral tracks, as in compact disks, may be preferred because of the continuity of the tracks.
In this case, the tracks need to be formed into a spiral form rather than a concentric form. However, in an optical disk in which the information is recorded both on lands and grooves and the tracks are spiral, it is necessary, after tracing the entire spiral formed of all the land tracks, for example, and groove tracks, to jump from the end of the land track spiral to the beginning of the groove track spiral. It is then necessary to access from the inner periphery to the outer periphery of the disk. Such an operation is time-consuming. In a disk which is divided into annular zones, the track jump is made from the inner periphery of the zone to the outer periphery of the zone, and the time for the jump is shortened but there is still a similar problem.
FIG. 23A and FIG. 23B show details of the header region 4 in a conventional optical disk wherein data is recorded on both groove and land tracks. FIG. 23A shows the case where headers are provided separately for the land and groove tracks, and addresses dedicated to the respective tracks are formed. FIG. 23B shows the case where headers are provided on an extension of a boundary between land and groove tracks, and each address is shared by the land track and the groove track separated by the boundary. In either case, the headers include address pits.
The header portion is formed of embossments (dents or projections) physically formed for representing the address information and the like of the sector preceded by the header, the sector being a unit for recording data. Specifically, pits having the same height as the lands, or pits having the same depth as the grooves are formed in the header portion where no tracks are formed.
There are several methods for forming prepits suitable for the land/groove recording configuration. Two principal ones are those shown in FIG. 23A and FIG. 23B.
In the configuration shown in FIG. 23A, dedicated prepits are provided for each sector of the land or groove track. Because the dedicated prepits can record various items of information, such as the one indicating whether the sector following the dedicated prepits is in a land track or a groove track, control in the optical disk drive device is facilitated. However, the width of the prepits must be sufficiently narrower than the track width. This means that the laser beam used for forming the tracks cannot be used for forming the prepits, and the fabrication of the medium is difficult.
In the configuration shown in FIG. 23B, the prepits are shared by the land and groove tracks adjacent to each other. The prepits can be formed by using the same laser beam as that used for forming the tracks, and by shifting the laser beam by xc2xd of the track pitch laterally of the track, i.e., in the radial direction of the disk. However, during writing or reading of the disk, the shared prepits cannot indicate whether the sector following the prepits is in a land track or groove track, so that the optical disk drive device must have a means to find whether a land track or groove track is being traced by the light spot, and the control in the optical disk drive device is difficult.
In the above-described optical disk allowing recording and reproduction, it is also necessary to solve the problem of the track offset. This relates to the fact that the one beam-and-push-pull method is used for the tracking, rather than a three-beam method. This is because the recording requires a greater laser power. Also, in the case of pit-forming recording, such as the one on a write-once disk, the side spots (used in a three-beam method) causes a disturbance to the tracking operation.
In a push-pull tracking, the tracking error is detected using the diffraction distribution of the light spot illuminating the pregrooves as shown in FIG. 24, and fed to the servo system, so that offset may occur due to the eccentricity of the disk or tilting of the disk. More particularly, an optical head 10 has a laser diode 66 emitting a laser beam, which is passed through a half-mirror 65 and an objective lens 67 to illuminate an optical disk 8 rotated by a disk motor 9. The reflected light beam from the light spot on the disk 8 is guided by the objective lens 67 and the half-mirror 65 and is received by a photodetector 11, and the tracking error is detected using the diffraction distribution of the light spot on the optical disk 8. The detected tracking error is used to control an actuator coil 64 for driving the objective lens 67.
For instance, a tilt of 0.7 degrees or an eccentricity of a 100 xcexcm (equivalent to lateral movement of the objective lens 62 of 100 xcexcm as indicated by broken lines in FIG. 24) causes shifting of a light distribution 12 on the photodetector 11, and hence an offset of 0.1 xcexc.
To prevent such a phenomenon, a drive device having higher mechanical and optical accuracy is used, and various other contrivances are adopted.
FIG. 25A shows the method of mirror surface correction in which a mirror surface part 7 is used. FIG. 25B shows the pit configuration of the optical disk used in combination with the wobble pits correction method.
In this method, wobble pit pits 68 and 69 being shifted in the radial direction of the disk by xc2xd of the track pitch are used. These methods are described in the following publications:
(1) Ohtake, et al. xe2x80x9cComposite Wobbled Tracking in the Optical Disk System,xe2x80x9d on pp. 181-188 in Optical Memory Symposium ""85, held on Dec. 12-13 1985, published by Optical Industry Technology Promotion Association,
(2) Kaku, et al. on xe2x80x9cInvestigation of compensation method for track offset,xe2x80x9d pp. 209-214 in Optical Memory Symposium ""85, held on Dec. 12-13 1985, published by Optical Industry Technology Promotion Association.
FIG. 26 shows a track offset correction circuit used in combination with a disk having the mirror surface portion 7 shown in FIG. 25A. A split photodetector 70 detects the tracking error by a push-pull method. An adder 15 adds the outputs of the two half-portions of the split photodetector 70 to produce a signal indicative of the total amount of light received, which corresponds to the total amount of light reflected from the disk. A differential amplifier 16 determines the difference between the outputs of the two half-portions of the split photodetector 70, to produce a signal indicative of the tracking error. A mirror surface detector 20 detects the mirror surface portion 7. A sample-hold circuit 23 samples and holds the tracking error signal when the light spot passes the mirror surface portion 7, and holds the sampled value as an offset information. A differential amplifier 47 determines the difference between the tracking error signal and the offset information. The output of the differential amplifier 47 indicates the tracking error having the offset removed.
FIG. 27 shows an offset correction circuit used in combination with a disk having wobble pits shown in FIG. 25B. A wobble pit detector 22 receives the output of the adder 15, and detects the wobble pits, i.e., produces a signal to a sample-hold circuit 23 when the light spot passes the wobble pit laterally shifted toward one side of the track, and produces another signal to a sample-hold circuit 24 when the light spot passes the wobble pit laterally shifted toward the other side of the track. Responsive to these signals (i.e., when the light spot passes the wobble pits 68 and 69), the sample-hold circuits 23 and 24 sample the output of the differential amplifier 16, and holds the sampled value. A differential amplifier 27 determines the difference between the outputs of the sample hold circuits 23 and 24, as an offset. An adder 28 adds the tracking error signal obtained at the differential amplifier 27 to the tracking error signal obtained by means of the ordinary push-pull method, to produce the tracking error signal from which the offset has been removed.
FIG. 28 illustrates the control characteristics for the case where a tracking error signal obtained by wobble pits and the tracking error signal by means of the conventional push-pull method are both used. Gl denotes a tracking open loop characteristic by means of the conventional push-pull method, and G2 denotes a tracking open loop characteristic by means of the wobble pits.
In this configuration, the guide grooves are discontinuous or interrupted at the mirror surface portion 7. With this configuration, a correction circuit for correcting the mirror surface offset, shown in FIG. 26, is required. The signals output from the two half-portions of the split photodetector 70 are input to the differential amplifier 16, which thereby produces a tracking error signal. The sum signal produced by the adder 15 is supplied to the mirror surface detector 20, which thereby generates a timing signal indicating the timing at which the light beam passes the mirror surface portion, and hence the signal should be sampled. The tracking error signal xcex94T produced by the differential amplifier 16 includes an error component xcex94Tg (error due to the photodetector 70 and the differential amplifier 16), a true tracking error xcex94Ts, and an offset component xcex4 due to various causes including the tilting of the disk, so that it is given by:
xcex94T=xcex94Ts+xcex94Tg+xcex4xe2x80x83xe2x80x83(1)
The sample-hold circuit 23 samples the tracking signal at the mirror surface portion 7, and holds the sampled value for each sector. The output of the sample-hold circuit 23 represents xcex94Tg+xcex4. Accordingly, in view of the equation (1), subtracting the output of the sample-hold circuit 23 from the output of the differential amplifier 16 at the differential amplifier 47 results in the true tracking signal xcex94Ts. In this way, a closed-loop servo system for achieving an accurate track following can be formed.
Another method of correction is a method using wobble pits. According to this method, a pair of sequences of pits shown in FIG. 25B are formed by alternately deflecting the light beam, using ultrasonic deflector, during fabrication of the original disk for mastering. During recording and reproduction, the amounts of the reflected light received when the light spot is passing the wobble pits on the respective sides are compared, to detect the tracking error. Specifically, a differential amplifier 27 shown in FIG. 27 determines the difference between the outputs of the sample-hold circuits 23 and 24 to obtain the tracking error. As shown in FIG. FIG. 29, when the light spot passes along a line closer to the center of the pit 68 on one side (top side in FIG. 25B) than to the center of the pit 69 on the other side (bottom side in FIG. 25B), an output signal illustrated by the dotted line is obtained. When the light spot passes along a line closer to the center of the pit 69 on the bottom side than to the center of the pit 68 on the top side, an output signal illustrated by the solid line is obtained. The difference obtained by subtracting the signal (amount of received reflected light) obtained when the light spot is passing the wobble pit 69 at the back, from the signal (amount of received reflected light) obtained when the light spot is passing the wobble pit 68 at the front, represents the magnitude of the tracking error and the direction of the tracking error. This means that the position at which the light spot passes is detected. Compared with the method relying on the diffraction distribution due to pre-grooves, the above-described method realizes a better servo system.
Another tracking method has been proposed, in which the feature of the above-described wobble pit method is maintained, and which is compatible with systems using conventional push-pull tracking method. The sector configuration in this system is composed of an index field with pre-pits shown in FIG. 23B, and data field which the user later utilizes. The index field is provided with address information, as well as wobble pits which may or may not serve also as a sector detection mark, and pre-grooves for tracking.
With such a configuration, the true tracking error is detected from the wobble pits, and the offset used in the push-pull tracking can be corrected. In this case, the open-loop characteristic of the tracking servo is such that the gain for tracking on the basis of the wobble pits is relatively large in the low-frequency region, and the gain for the tracking on the basis of the push-pull method is relatively large in the high-frequency region, as shown in FIG. 28. As a result, data can be recorded and reproduced, while the light spot is maintained on the center of the track, regardless of the drive device used, and compatibility between the recorded disk and the drive device can be preserved.
With the above-described optical disk drive device, information is recorded on lands and grooves to increase the recording density. In such an optical disk, to avoid the complexity of operation during disk-mastering, it was necessary to provide address pits in the header portion, being xc2xd pitch shifted in the radial direction from the information track, so as to enable reading during tracing of the land track or groove track. Each header is therefore shared by the land and groove, whether the light spot is scanning a land or a groove is not known from the address alone.
The sequences of pits for recording the address information are disposed at positions shifted with respect to the track center, so that when the signal amplitude is lowered or track offset occurs, it is difficult to obtain information reliably. In particular, when the address information is incorrectly read, the recording and reproduction of information over the entire sector cannot be achieved, and fundamental information as to whether the light spot is scanning a land or a groove, or in which zone the light spot is scanning, or the like may become incorrect, and the disk rotation control, tracking control, or the like may fail.
In the case of a disk of a spiral configuration in which a land and a groove alternate every revolution, it is necessary to judge whether the sector following the header is in a land or a groove. This judgment must be reliable, since if this judgment is erroneous, failure of tracking may occur.
Furthermore, because the tracking polarity is reversed every revolution, the polarity of the tracking error signal is reversed every revolution, and error in counting using the tracking error signal during track access, or failure in pull-in at the time of track jump may occur.
In addition, during access, when the boundary between adjacent zones is not known, CLV (constant linear velocity) control is effected after tracking onto the target track, so that the settling requires time. To avoid this problem, a detecting means which can detect the tracking polarity and the current zone position even when tracking is not attained.
The present invention has been achieved to solve the problems described above, and its first object is to provide an optical disk in which recording can be made on both of lands and grooves, and having recognition patterns in the headers for the information sectors, which can be distinguished clearly from recorded data, and which permits reliable detection with an error rate lower than recorded data.
A second object is to provide recognition patterns in the headers which enable identification of the zone to which the sector belongs, and judgment as to whether the sector is in a land or a groove.
A third object is to provide an optical disk and an optical disk reproducing device by which the recognition patterns in the headers can be decoded even when tracking is not achieved, and disk rotation control can be achieved during access.
A fourth object is to provide an optical disk and an optical disk reproducing device by which the recognition patterns in the headers can be reproduced and decoded even when tracking is not achieved, and the track count error during access can be reduced, and stable pull-in operation to the target track is enabled.
According to one aspect of the invention, there is provided an optical disk having information recording tracks in the form of land and groove tracks, the disk being divided into a plurality of annular zones, each revolution of the information recording track belonging to one of the zones depending on the position in the radial direction of the track,
each revolution of the information recording track being divided into a plurality of sectors of a unit length of information recording in the direction of the scanning,
the disk having a header portion at the head of each sector,
the header portion including a recognition pattern which is formed of a sequence of pits having a pattern which is not used as a pattern for data or address in the information recording part, in the modulation method used.
The disk may be of a land/groove single-spiral configuration in which land tracks and groove tracks are connected at connecting points, occurring every revolution, so that land and groove tracks alternate every revolution along a continuous spiral.
It may be so arranged that the header portion for each sector has a plurality of sub-headers, including an address of the sector, and first and second recognition patterns,
major part of the sub-headers including the address of the sector, and the first recognition pattern are provided, being shifted in one radial direction by half a track pitch with respect to the center of the track of the sector, the second recognition pattern provided being, being shifted in the other radial direction by half a track pitch with respect to the center of the track of the sector.
With the above arrangement, sequences of information which are not included in the modulation patterns used for the information recording are used for the recognition patterns. The pattern matching during reproduction of the recognition patterns can be effected reliably, and discrimination reliable between the recognition patterns and recording data can be made. Furthermore, a plurality of subheaders including a pair of recognition patterns and the address of the sector are disposed, with the first one of the recognition patterns and the address being shifted by half a track pitch in one lateral direction, with the other recognition pattern being shifted in the other lateral direction. Accordingly, they can be used for detection of track offset, and providing of the plurality of pairs of recognition patterns enables comparison, and prevents erroneous detection.
The recognition patterns used for determining the timing of detection of the address data, and timing of detection of wobble pits (formed of the subheaders for the sector which is scanned after the header, and the subheaders for the sector in the next track) and mirror surface part are of a sequence of pits having a pattern which is not used for information recording. As a result, judgment as to whether the reproduced signal represents a recognition pattern or the recorded information can be made reliably. The detection of the address data and tracking offset can be made reliably, and the tracking operation free from offset can be achieved.
A mirror surface part may be provided at the back of the recognition pattern.
The recognition pattern may be formed of pits of different lengths, the minimum length being longer than the minimum pit length of the signal of the data recorded in the information recording part.
With the above arrangement, the information for the recognition patterns can be reproduced even in a state of track deviation.
Also, even when the reproducing spot size is enlarged due to defocusing, because of vibration of the device, for instance, information can be reproduced with a low error rate, and the stability in the offset correction operation and polarity reversal operation is improved.
The recognition patterns in the header may contain an identification code indicating the zone to which the sector belongs.
With the above arrangement, the identification of the zone can be made not only during recording and reproduction of information, but also during track access. Specifically, such identification of the zone can be made even at the time of the servo pull-in when the tracking operation is not yet stable, and when the tracking servo is not applied, during track access.
The recognition patterns in the header may contain an identification code indicating whether the information recording part of the sector is a land or a groove.
With the above arrangement, the identification as to whether the sector is a land or a groove can be made not only during information recording and reproduction, but also during track access.
As a result, in a disk in which the land and groove alternate every revolution to form a continuous track, a continuous track crossing signal, similar to that obtained with the prior art spiral disk, can be obtained.
The headers may be aligned in the radial direction, and the interval between the recognition patterns may be varied.
The interval between the recognition patterns may be varied by varying the length of the VFO.
According to another aspect of the invention, there is provided an optical disk drive device using an optical disk having information recording tracks in the form of land and groove tracks, the disk being divided into a plurality of annular zones, each revolution of the information recording track belonging to one of the zones depending on the position in the radial direction of the track,
each revolution of the information recording track being divided into a plurality of sectors of a unit length of information recording in the direction of the scanning,
the disk having a header portion at the head of each sector,
the header portion including a recognition pattern which is formed of a sequence of pits having a pattern which is not used as a pattern for data or address in the information recording part, in the modulation method used,
the device comprising:
means for generating a light spot and causing the light spot to scan along the track;
means for receiving light reflected from the disk;
means for detecting the amount of reflected light; and
a pattern matching circuit responsive to the means for detecting the amount of reflected light, for detecting the recognition pattern.
According to a further aspect of the invention, there is provided an optical disk drive device using an optical disk in which the information recording tracks are present both on lands and grooves, and the disk being divided into a plurality of annular zones, the disk having an identification code in each header indicating the zone to which the header belongs,
the device comprising:
means for generating a light spot and causing the light spot to scan along the track;
means for receiving light reflected from the disk;
means for reproducing a signal based on the reflected light;
means for reading said identification code from the reproduced signal during track crossing, during track access or when the tracking servo is not operating; and
means for controlling the rotational speed of the optical disk on the basis of the result of the reading.
During track access or when the tracking servo is not operating, the recognition pattern can be reproduced from the reproduced signal during track crossing, and the rotational speed of the optical disk can be controlled on the basis of the result of the reproduced identification code.
As a result, the settling of the motor can be accomplished promptly, and the access time can be shortened in a disk of zone CLV system. In particular, with a phase-change type disk, the recording depends of the linear speed. By shortening the settling time, the average data recording rate can be improved.
According to a further aspect of the invention, there is provided an optical disk drive device using an optical disk in which land and groove tracks alternate every revolution to form a continuous information track, and the disk being divided into a plurality of annular zones,
the disk having recognition patterns including an identification code indicating whether the header is at a connecting point between a land and a groove,
the device comprising:
means for generating a light spot and causing the light spot to scan along the track;
means for receiving light reflected from the disk;
means for reproducing a signal based on the reflected light;
means for reading the identification code from the reproduced signal during track crossing, when the track servo is not operating, and
means for performing track pull-in after switching the polarity of the tracking error signal on the basis of the reading.
With the above arrangement, the track pull-in operation in a disk having alternating lands and grooves is facilitated.
That is, erroneous pull-in to an adjacent track due to the difference in the polarity can be prevented, and the access to the target address can be achieved accurately.
According to a further aspect of the invention, there is provided an optical disk drive device using an optical disk in which lands and grooves alternate every revolution to form a continuous information track, and the disk being divided into a plurality of annular zones,
the disk having recognition patterns including an identification code indicating whether the header is at a connecting point between a land and a groove,
the device comprising:
means for generating a light spot and causing the light spot to scan along the track;
means for receiving light reflected from the disk;
means for reproducing a signal based on the reflected light;
means for reading the identification code from the reproduced signal during track access, and
means for performing track count from the tracking error signal, after switching the polarity of the tracking error signal on the basis of the reading.
With the above arrangement, continuous track crossing signal is obtained, and the count error (especially, during a high-speed access) is reduced.
According to a further aspect of the invention, there is provided an optical disk drive device using an optical disk having information recording tracks in the form of land and groove tracks, the disk being divided into a plurality of annular zones, each revolution of said information recording track belonging to one of the zones depending on the position in the radial direction of the track,
each revolution of the information recording track being divided into a plurality of sectors of a unit length of information recording in the direction of the scanning,
the disk having a header portion at the head of each sector,
the header portion including a recognition pattern which is formed of a sequence of pits having a pattern which is not used as a pattern for data or address in the information recording part, in the modulation method used,
the header further including a VFO,
the device comprising:
means for generating a light spot and causing the light spot to scan along the track;
means for receiving light reflected from the disk;
means for reproducing a signal based on the reflected light;
means responsive to the reproduced signal corresponding to the VFO, for generating PLL clock pulses;
means for counting the clock pulses; and
means for responsive to the result of the counting, for outputting a signal at a timing at which the light spot scans the wobbling address pits, or the mirror surface part.